On $\Delta$-Transforms

Abstract

Any set of two legs in a Gough-Stewart platform sharing an attachment is defined as a Delta component. This component links a point in the platform (base) to a line in the base (platform). Thus, if the two legs, which are involved in a Delta component, are rearranged without altering the location of the line and the point in their base and platform local reference frames, the singularity locus of the Gough-Stewart platform remains the same, provided that no architectural singularities are introduced. Such leg rearrangements are defined as Delta-transforms, and they can be applied sequentially and simultaneously. Although it may seem counterintuitive at first glance, the rearrangement of legs using simultaneous Delta-transforms does not necessarily lead to leg configurations containing a Delta component. As a consequence, the application of Delta-transforms reveals itself as a simple, yet powerful, technique for the kinematic analysis of large families of Gough-Stewart platforms. It is also shown that these transforms shed new light on the characterization of architectural singularities and their associated self-motions.